Ukraine crisis: Petro Poroshenko orders army ceasefire after agreement reached with rebels

The ceasefire must be observed by the separatists too and be monitored by international observers from Europe's OSCE security watchdog, he said in a statement published on his website.

"Human life is the highest value and we must do everything possible and impossible to end the bloodshed and the suffering," said Poroshenko, who has spent the last two days attending a NATO summit in Wales.

The talks to bring a much-anticipated ceasefire to the fighting​ began Friday at 7 a.m., even as the rebels kept pressing their offensive against a strategic port city.

• LIVE | Latest updates from the NATO summit
• NATO, Ukraine optimistic about potential ceasefire
• 13 Canadian soldiers to be included in Ukraine peacekeeping exercise

Russian President Vladimir Putin said this week he had broadly agreed on steps toward a resolution of the conflict with Poroshenko and set out a seven-point proposal end to end the five-month-old conflict.

Heavy shelling around Mariupol

Despite the development, a senior rebel leader said the ceasefire deal did not change the desire of pro-Russian rebels in eastern Ukraine to break away from Kyiv.

"The ceasefire does not mean the end of (our) policy to split (from Ukraine)," Igor Plotnitsky, the leader of the self-proclaimed Luhansk People's Republic, told reporters.

Earlier, the rebels pressed ahead with their southeast offensive Friday on Mariupol, a key port of about 500,000 people that lies on the Sea of Azov, between Russia to the east and the Crimean Peninsula to the west, which Russia annexed in March.

Associated Press reporters heard heavy shelling Friday morning north and east of Mariupol, which appeared to indicate that rebels have partially surrounded the area and are probing its defences.

• MAP | Recent clashes in Ukraine

The seizure of Mariupol would give the rebels a strong foothold on the Sea of Azov and raise the threat that they carve out a land corridor between Russia and Crimea. If that happens, Ukraine would lose another huge chunk of its coast and access to the rich hydrocarbon resources the Sea of Azov is believed to hold. Ukraine ready lost about half its coastline, several major ports and untold billions in Black Sea mineral rights with Russia's annexation of Crimea. 

Alexander Zakharchenko, the leader of pro-Russian rebels in Donetsk, attends talks on ceasefire in Ukraine in Minsk, Belarus on Friday. The peace talks began Friday in the Belarusian capital even as the rebels kept pressing their offensive against a strategic port city. (Associated Press)

"Mariupol is a strategic point. If we lose it then we could lose the entire coastline, the whole south of Ukraine," said Tatyana Chronovil, a prominent Ukrainian activist at a mustering point for the volunteer Azov Battalion on the eastern edge of the city.

The rebel offensive follows two weeks of gains that have turned the tide of the war against Ukrainian forces, who until recently had appeared close to crushing the five-month rebellion in the east. Ukraine and the West say the rebel counterattack was spearheaded by regular Russian army units, a charge the Kremlin has denied.

According to Ukrainian military spokesman Lysenko, about 2,000 Russian servicemen have been killed so far in the conflict. It was not possible to independently confirm the figure. 

NATO rapid response force

For all the upbeat assessments, however, NATO Secretary-General AndersFogh Rasmussen was still skeptical of Russian motives. "What counts is what is actually happening on the ground," he said at the NATO summit in Wales on Thursday. 

Ukrainian forces pounded pro-Russian rebels to the east of the port of Mariupol on Friday, hours before envoys from Ukraine and Russia were expected to announce a ceasefire as the starting point for a wider peace plan. (Vasily Fedosenko/Reuters)

"I have to say that previously we have seen similar statements and initiatives and they have been a smoke screen for continued Russian destabilization of the situation in Ukraine."

Seeking to counter Russian aggression, NATO leaders approved plans Friday to create a rapid response force with a headquarters in Eastern Europe that could quickly mobilize if an alliance country in the region were to come under attack. 

NATO Secretary General Anders Fogh Rasmussen said the new unit would send a clear message to potential aggressors, namely Russia.

"Should you even think of attacking one ally, you will be facing the whole alliance," he declared as a two-day NATO summit in southern Wales drew to a close.